Effect of magnetite supplementation on mesophilic anaerobic digestion of phenol and benzoate: Methane production rate and microbial communities

Anaerobic sequential batch tests treating phenol and benzoate were conducted to evaluate the potential of magnetite supplementation to improve methanogenic degradation of phenol and benzoate, and to identify active microbial communities under each condition. Specific CH₄ production rates during anaerobic digestion were 218.5 mL CH₄/g VSS/d on phenol and 517.6 mL CH₄/g VSS/d on benzoate. Magnetite supplementation significantly increased methanogenic degradation of phenol by 9.0-68.0% in CH₄ production rate, and decreased lag time by 7.9-48.0%, with no significant reduction in CH₄ yield. Syntrophorhabdus, Sporotomaculum, Syntrophus, Syntrophomonas, Peptoclostridium, Soehngenia, Mesotoga, Geobacter, Methanosaeta, Methanoculleus, and Methanospirillum were revealed as active microbial communities involved in anaerobic digestion of phenol and benzoate. Magnetite-mediated direct interspecies electron transfer between Geobacter, Peptoclostridium, and Methanosaeta harundinacea could contribute to this improvement.